1. Field of the Invention
The present invention relates to an imaging apparatus and an exposure controlling method, which are used in a digital camera with an automatic exposure adjusting function.
2. Description of the Related Art
Today, digital cameras with an automatic exposure adjusting function are widely used. In these digital cameras, exposure conditions are adjusted based on brightness of an object image obtained on assumption that a reflectance ratio of the object in the natural conditions is 18%.
But these digital cameras have drawbacks that when a blackish object whose reflectance ratio is lower than 18% or a whitish object whose reflectance ratio is higher than 18% is photographed, the exposure conditions are set to over exposure conditions or under exposure conditions compared with the appropriate exposure conditions, and as a result an appropriately exposed picture cannot be obtained.
A camera was proposed, which is capable of adjusting the exposure conditions based on the reflectance ratio of the object (Refer to Japanese Patent Application Hei8-328069 A). The camera has a built-in flash unit, and measures the reflectance ratio of the object and adjusts light volume produced by the flash unit based on the measured reflectance ratio, thereby obtaining an appropriately exposed picture of the object even though the reflectance ratio of the object is extremely high or low.
But the camera disclosed in above Japanese Patent Application Hei8-328069 A calculates the reflectance ratio of the object based on the light volume of light produced by the flash unit and the light volume of light received by a light receiving device. Therefore, all the light produced by the flash unit must be applied to the object, and the reflectance ratio of the object can be calculated correctly only in the state where all the light produced by the flash unit can be applied to the object.
The camera involves a problem that the flash unit cannot emit light under the appropriate exposure conditions in the state other than the state where all the light produced by the flash unit is applied to the object. As a result, appropriate exposed pictures cannot be obtained with the above described camera.
The present invention has been made to solve the problems involved in the conventional technique, and has an object to provide an imaging apparatus and an exposure controlling method, which are capable of setting appropriate exposure conditions based on the reflectance ratio of the object.